Effects of humidity ranging 50%-60% during mid and late flower.

[Bulénath]

Aloha everyone!
It seems common knowlede that flowering plants prefer humidity ranges of 20% -40% during flower. Some growers say 50% humidity is acceptable, but not optimal during flower.

The only logical reason for this optimal humidity range seems to be the mold and mildew factor. Mold and mildew can thive within the dark, moist bud clusters.

But other than the mold and mildew factor, what other bennefits are provided when your flower chamber's humidity are between 20%-40% during mid-late flower?

Are there any other dowsides to humidity over 50% during flower?


I appreciate all advice, thank you eveyone!

 

[Hereward]

Well, you're right that the primary concern is avoiding mold. It's also said that plants respirate easier in moderate humidity.

The other benefit of low humidity is based on a theory that cannabis in its flowering cycle will secrete more resin in low humidity conditions. Plants naturally do this to protect themselves from drying out, and Indica strains in particular have evolved into this function very well over thousands of years. This is supposedly why the traditional hashish making regions of the world, (morrocco, lebanon, turkey, egypt, etc.), also happen to be very dry and arid; and are traditional regions of many indica "landrace" varieties.

More resin=more thc=more happy!

However, in my experience, flowering cannabis does just fine in mid-range RH, like up to 60%. Most growers I've known haven't gotten too concerned over RH unless it got much over 60-65% in flowering, but you're right: tolerable, not really optimal.

 

[GMT]

we grow in the uk and it gets pretty wet here

 

[mtnjohn]

you know iv'e been growing for a long while and i have never once checked my
RH...........only had mold 2 times years ago..now i keep my ventilation on 24/7
....no mold since
mj

 

[Fritz the Cat]

The lower the rh the more your plants need to transpire.the more water /nutes it pulls up the more unbalanced your plants are. We run ours at 65-70% Rh, learned that from Krusty. No mold.

 

[Guest]

Good ol'Krusty.
The flower room usually runs at 78 deg F, 50% RH, and the mom cab is usually running lower than this (I was tweaking ventilation).



Cheers.

See ya in chat...........

 

[Bulénath]

Aloha everyone and thank you for the responses.

Hereward, I really enjoy reading you response. Thank you for the input! I had no idea that plants secrete more resin to protect against dry conditions. Perhaps this is why many profesional growers feel the lowest temperature and humidity should be highly considered during the last 2-3 weeks of flower.

Aloha!

 

[pico]

if humidity is too high it can greatly reduce uptake of co2. co2 is required for photosynthesis

 

[MaxYield]

So, if you want to optimize your plant grow, should you be aiming for 20% RH or less or closer to 40%??

Another thing, what tricks do yall have to maintain your RH at the level you want?? Is good ventilation enough, is the dehumidifier mandatory or is their any other tricks to help control humidity?

 

[Guest]

see my problem is that at night i turn vents off so that the cold air doesnt come in and get the temps to low. do you think it would be better if i rigged just to have the exit vent running all the time to pull out humidity and left the intake vent off? this is only a problem i run into durring the winter since its warm the rest of the year here.

 

[mtnjohn]

^^^^^oh yeah...ventilation 24/7
mj

 

[Guest]

So, if you want to optimize your plant grow, should you be aiming for 20% RH or less or closer to 40%??

you want rh closer to 50-60%.. I keep mine between 55-60 with lots of airflow through the canopy. No mold ever.

 

[MTF-Sandman]

^^Yeah...low RH invites insects, so I would definitely try to keep it above 40%. I've had it as high as 75% without molding, but I had LOTS of airflow.

How to keep your RH constant will depend on many factors like your climate, your ventilation system, air circulation to name a few. Dehumidifiers work great for sealed areas, but if you're venting an area the dehum will end up running 24/7 trying to keep up with all the moisture being sucked into the room from the intake...and by the time it has a chance to dry the air, the air is sucked outta the room.

 

[Guest]

My RH has always been 15-30% throughout the entire process. I also turn all my ventalation off at night there are still fans going within my abnormally large room for my 400 though... never had mold, clean crystally buds.

Anyways, RH may be beneficial but it does not make that big a difference, except on things like mold, poor circulation, or really humid locations, indoors at least.

I will say however with my lower RH there are a bit more pests, but I will take fungus flies over bud rot/mold in a heartbeat.

 

[Guest]

Here are some links that I got from knna over at CW regarding vapor pressure deficit and humidy... lots of people underestimate humidity in regards to growing... this should open your eyes and mind


Respiration and Humidity Powerpoint presentation
Answers.com VPD

VPD Calculation Method
Humidity in Greenhouses
Department of Agriculture - Use search for lots of info


Hope this helps Actual thread at CW

 

[tokersmoke]

RH is def important.I wouldnt consider growing if i didnt at least monitor the humidity.got to stay at 65-70 in veg and 40-50 in flower.In my room the dehuey can pull 50 pints of water in less then 24 hours! if i didnt have the dehuey on i would surely get mold.